This invention relates to a data processing device and a data recording method which are suitable for use in a data recording system for encoding data in accordance with a synchronizing signal.
For digital image compression processing represented by the MPEG (Moving Picture Experts Group) standard or the like, it is assumed that an input standard video signal is encoded in accordance with a predetermined rule. Conventionally, an analog video signal that is actually input is often a nonstandard video signal in the case where a video signal of only one field exists, as in game equipment, or in the case where the temporal length of the frame varies, as in the varying-speed reproduction by a VCR (video cassette recorder), or in the case where the frame is made discontinuous by switching the channel of the input signal. Therefore, when carrying out digital image compression processing by converting an analog video signal to a digital video signal, encoding oftentimes cannot be carried out.
On the other hand, in a conventional technique, if a nonstandard video signal is detected, encoding may be temporarily interrupted and then resumed from a frame of standard video signal without encoding the frame of the nonstandard video signal. That is, conventionally, an asynchronous video signal can be dealt with by temporarily stopping the encoding process. However, this technique of temporarily stopping the encoding process has the drawback that video data to be encoded and output becomes discontinuous.
In another conventional technique, when a field video signal is a nonstandard video signal, processing to reduce or increase the number of lines may be carried out, thus converting the nonstandard video signal to a standard video signal and then encoding the standard video signal. This technique of controlling the number of lines, however, suffers from the drawback that a different image from the original input image is encoded.
In a further conventional technique, an input video signal may be temporarily stored in a frame memory and a master clock which is asynchronous with a synchronizing signal at the time of input may be generated by a crystal oscillator or the like. The input video signal is read out by using the synchronizing signal and the master clock and is then encoded. However, in this technique of reading out a video signal using a synchronizing signal and a master clock and thus encoding the video signal, since the video signal is read out from the frame memory using a master clock which is not synchronized with a synchronizing signal at the time of input, the quantity of delay of the video signal in the frame memory differs between when the video signal is read out using the synchronizing signal and when the video signal is read out using the master clock. In the case where the quantity of delay is not constant as described above, the quantity of delay with respect to an audio signal that is input simultaneously with the video signal is undefined and synchronization between the video signal and the audio signal cannot be achieved.